The successful operation of the Space Shuttle program currently operated by the National Aeronautics and Space Administration has been aided by detailed preparation in anticipation of possible causes of failure and providing corrective avenues in the eventuality of any foreseeable problems. One such provision is the development of repair techniques for replacing of damaged or lost HRSI tiles by the astronauts during the orbital portion of a space mission. A Surface Attachment Assembly (SAA) has been developed for this purpose and is the subject matter of NASA Invention Disclosure No. LAR 12894-1 entitled "Hot Melt Adhesive Attachment Pad" and made by the present inventor, and others, and filed in the U.S. Pat. Office, Ser. No. 516,087, on July 22, 1983. This system utilizes a Shuttle Work Restraint Unit (SWRU) consisting of a scaffolding or platform releasably attached to the vehicle exterior, i.e., to the thermal protective tiles or other areas of the vehicle to permit extra vehicular work by the astronaut. This work restraint unit permits more freedom of movement by the astronauts in making repairs to the vehicular exterior or for other work requiring the use of both hands. The work restraint unit is provided with one or more surface attachment assembly pads that serve as the releasably attached contact points for the work restraint unit. In the embodiment to be described herein one pad unit consists of three surface contact pads attached to the work restraint unit and serving as a releasably attachment for the unit with the vehicle surface. Thus, by securing the work restraint unit to a particular segment of the vehicle exterior via the releasably surface contact pads, needed work on the vehicle at a specific location may be conducted and when completed the releasable contacts moved to a different area of the vehicle. Thermoplastic adhesives that soften at controlled elevated temperatures and resoldify when the temperatures are decreased have proved of adequate strength for these purposes. By providing heating and cooling mechanisms in the surface attachment pad faces, a charge of hot melt thermoplastic adhesive provided on the pad surface is heated and cooled selectively to provide the attachment and release of the work restraint unit at the control of the astronaut operator. One problem that has arisen in the use of this attachment-release mechanism however, is that the hot melt adhesive charge is depleted after a number of attachment-release sequences and the attachment must be recharged with additional adhesive. Problems arising in accomplishing this recharge load process under the adverse spatial vacuum conditions has led to the present invention.
It is therefore an object of the present invention to provide an article of manufacture that permits accurate positioning of hot melt type adhesive.
Another object of the present invention is to provide a process for recharging a hot melt adhesive to an attachment pad.
A further object of the present invention is an article for protectively packaging individual hot melt adhesive charges until ready for use.
An additional object of the present invention is a recharge assembly for a hot melt adhesive attachment pad.
According to the present invention, the foregoing and additional objects are attained by providing a charge or film of hot melt thermoplastic adhesive sandwiched between two layers or sheets of protective film strips that extend beyond the film of hot melt adhesive. At least one of the film strips is provided with a pressure sensitive adhesive coating to adhere to the film of hot melt adhesive and the other film strip to form the sandwich. Suitable non-adhering tab ends are provided on each end of both film strips to facilitate separation of the film strips and expose a surface of the hot melts adhesive. For use, this exposed surface of adhesive is disposed abutting a surface attachment pad and retained in position thereon by the remaining pressure sensitive film strip while heated to the melt or softening temperature of hot melt adhesive. The adhesive is then cooled to solidifying temperature and, thus, becomes permanently affixed to the surface attachment pad. Upon each attachment/release of the surface attachment pad some of the hot melt adhesive charge is lost and after a number of such uses the charge must be replaced. The recharging process is difficult to perform under the adverse spatial vacuum conditions without the use of the present invention.